Astronomers Predict Spectacular Meteor Shower Show in 1998

[Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>]

Royal Astronomical Society Press Notices

Date: 8 April 1997
Issued by: Dr Jacqueline Mitton
RAS Public Relations Officer
Phone: Cambridge ((0)1223) 564914
FAX: Cambridge ((0)1223) 572892
E-mail: jmitton@ast.cam.ac.uk

Astronomers Predict Spectacular Meteor Show For 1998

The Leonid meteor shower is expected to produce a particularly spectacular
display in November 1998 according to Professor Iwan Williams of Queen Mary
and Westfield College, University of London, who has been studying what is
known about the stream of meteoroids in space which is responsible for the
shower. Professor Williams presents his findings at the UK's National
Astronomy Meeting at Southampton University on Friday 11th April 1997. The
Leonids produce grand displays about every 33 years. The last time was in
1966, but 1998 could be better than 1999, Professor Williams says.

Meteor streams are formed from the dust grains released by the nucleus of a
comet when it gets near to the Sun and becomes active. If the Earth's orbit
crosses through the meteor stream, we experience a meteor shower. Over time,
the dust grains spread slowly round the comet's orbit. When they are
distributed around the whole of the orbit, the same number of meteors are
seen at about the same time each year. However, this is not the case with
the Leonids.

The Leonids are dust from comet Temple-Tuttle, discovered in 1865, but that
dust is still in a large clump close to the comet. It has not had enough
time to spread all round the orbit. That means that the Leonids produce
large numbers of meteors when Earth is near the comet -- about every 33 years
-- and are rather sparse or non-existent at other times.

Professor Williams says that his calculations suggest 'the display will be
spectacular but not awesome, that is several thousand meteors per hour
rather than tens or even hundreds of thousand as has been the case on some
occasions in the past. He also thinks 1998 will possibly be the best year
rather than 1999 since the comet's closest approach to Earth is between the
two dates but closer to November 1998.

The start of the serious scientific study of meteors is generally attributed
to the spectacular display produced by the Leonids in November 1833. It was
studies of this shower that led to the observation that the meteors appeared
to originate from a single point, or radiant, in the sky. This was correctly
interpreted as signifying that the meteoroids move on essentially parallel
tracks in the solar system, as a stream. In the case of the Leonids, the
radiant is in the constellation Leo -- hence the name of the shower.

The mathematician John Couch Adams (1819-1892) (who also predicted the
existence of the planet Neptune) studied changes in the Leonid stream and
concluded that the orbital period of the Leonid meteors was about 33.25
years. This was remarkably similar to that of the newly discovered Comet
Temple-Tuttle. It was also soon realized that spectacular displays of the
Leonid stream had occurred at the same interval. Good displays were seen in
1799, 1833 and 1866. Since then, spectacular displays occurred around 1900
and in 1966.

Contact

     Professor Iwan Williams, Astronomy Unit, Queen Mary and
     Westfield College, London E1 4NS. Phone 0171-975-5452.
     E-mail: I.P.Williams@qmw.ac.uk

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